Processing thermoplastic rubber gel sealants in a cost effective and efficient manner has presented its challenges. As technology progresses, sealants will be subjected to increasingly higher temperature environments and more demanding performance requirements. There has been, and there presently exists, a need for high performance sealants to meet these demands. For example, there is an increasing need for high service gel sealants for use in outdoor energy transmission applications and for use near or inside engine compartments.
In particular, closure systems are used to protect internal components from degradation caused by external environments. For example, components related to the connections of fiber optics cables, coaxial cables, and copper cables are often enclosed in closure systems. Examples of commercially available closure systems include Fiber Optics Splice Closures (FOSC), the Outdoor Fiber Drop Repair (OFDR), the Outdoor Fiber Distribution Closure (OFDC), and the Fiber optic infrastructure System Technology (FIST). Additional commercially available closure systems include copper joints such as Mechanical Joint Closure (MMC), Toolless Torchless Reentrable Closure (TTRC), and Coax connector closures (GSIC) available from TE Connectivity. These types of closures can be used in aerial, pedestal, and underground environments. Other closure systems are commercially available for use with communication and energy transmission cables.
Closure systems typically include internal components such as fiber organizers, cable seals and termination devices, drop cable seals for a number of drops with drop cable termination devices, universal splice holders for a number of splices, and copper and coax connections. Cable joints may be subject to environmental factors such as varying moisture levels, heat and cold, and exposure to other chemical substances, so the internal components and connections will require appropriate protection from these elements. The closure systems are preferably protected from damage with a sealant of some sort. Conventional sealants, however, suffer from a number of drawbacks that make them less suitable for certain closure systems.
Sealants are often used for insulation and for protection against water, corrosion and environmental degradation, and for thermal management. A number of sealants are known but currently available sealants have certain drawbacks and disadvantages that make them inadequate for specific uses and for use in contact with certain materials. In particular, there is an unmet need for sealants that are suitable for the latest types of fiber optic and electronic closure systems.
Suitable sealing systems for closures are needed for use with a variety of different cables. Traditionally, thermoplastic elastomer gels (TPEGs) have been used as sealants in certain applications due to their unique properties. TPEGs have provided many years of reliable in-field performance for applications requiring a low maximum service temperature of approximately 70° C. TPEGs may comprise a styrene ethylene/butylene styrene (“SEBS”) copolymer swollen with an oil softener (e.g., mineral, synthetic, or vegetable oil softeners). A problem, however, with thermoplastic gels used as sealants, and in closure systems in general, is that they often contain high amounts of mineral oil. Conventional thermoplastic gels typically exhibit 20 to 30 wt % oil bleed out. Accordingly there exists an unmet need for gels, sealants, and closure systems with suitable hardness, viscoelastic properties, long-term performance (e.g., >20 years), amongst other properties, including low oil bleed out, better processability by improved melt viscosity, lower shrinkage, and better thermal conductivity.